Blown CIM?

[Michael Hill]

Originally Posted by FrankJ

Yes it possible to blow them. Harder to tell if they are partially degraded. Many teams use new motors in their competition bots for that reason.

One possibility would be to use a good ohm meter & slowly turn the motor and watch the coil resistance & compare it to a new motor. That will only show a badly degraded motor though. like one with open windings.

Another possibility would be to run it with a known load & compare its speed & current draw against a new motor.

I've never had much luck with using an ohmmeter on a CIM. There has always been too much relative variation to get much of a measurement. I generally get somewhere between 0.4 - 3 Ohms (this is from memory right now) with a new CIM. I'm sure it has to do with the windings on the CIM and the shaft wanting to settle into a finite number of positions because of the magnetic field. Perhaps an ESR or LCR meter might be a better tool to measure the impedance with magnetics. I was just using a Fluke 87V DMM.